/**
 * @api {get} /users/captcha 图片验证码
 * @apiName captcha
 * @apiGroup captcha
 *
 * @apiSuccess {img} img <img src="/users/captcha" onclick="this.src=this.src+'?'" style="cursor: pointer">.
 *
 * @apiSuccessExample 成功-响应:
 *     HTTP/1.1 200 OK
 */

/**
 * @api {get} /users/captcha/:vcode 验证图片验证码
 * @apiName validateCaptcha
 * @apiGroup captcha
 *
 * @apiParam {String} vcode 验证码.
 *
 * @apiSuccess {Number} code 状态码.
 * @apiSuccess {String} msg 信息.
 * @apiSuccess {Object} data 响应数据.
 *
 * @apiSuccessExample 成功-响应:
 *     HTTP/1.1 200 OK
 */